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Talked to the machine shop today. If I can't get to 0.040 to 0.045 quench with a piston and head gasket combination I'll take 0.010 to 0.015 off the deck.Your SBC block deck height dimension should be 9.025". I would start with that, and do the math to learn what your piston deck height will be.

And for clarity...... are you building a 6.3L?
If building a Q/E 5.7L, I would shoot for a Quench dimension of .038", and if building a Q/E 6.3L, I would shoot for a Quench dimension of .043" or so.

Like I said before there's dosen't seem much I can do with timing. Unless anyone knows someone who has hacked the 555 ecm? There don't seem to be any "block boxes" for the 555.

OK..... you can increase the TA (total advance) simply by increasing the BASE or Initial advance.
In other words, if you increase BASE by 3*, you will have increased TA by that same 3*.

However, increasing BASE may create "bucking" during cranking! If so, then yes...... the controller would need to be altered so that the OEM BASE advance can be maintained, yet allow for more Progressive and TA.

A good Quench Effect (via correct piston profile) and a good quench dimension should allow for an ignition advance of approx 32* @ 3,200 RPM, placing the LPCP @ 12* to 14* ATDC.

Heads up...... you may find a few machine shops who will Foo Foo the Quench Effect idea, and tell you that it's not necessary. If so, I would suggest finding another shop.

The first SBC V-8 incorporated a quench effect. It wasn't until the early 70s when the GM engineers came up with the full dished piston in an effort to reduce emissions.
Also, the Chrysler Wedge Head enthusiasts have been using the Quench Effect for years and years.

Comment

Your correct the only way to move the timing is in the ecm. I don't seem to have a cam sensor just crank Not sure I want to bet a $700 reflash on +3 or so timing?
Why .043 on the quench are you worried about piston rock?

You're correct the only way to move the timing is in the ecm. I don't seem to have a cam sensor just crank Not sure I want to bet a $700 reflash on +3 or so timing?

OK.... if the Progressive and the TA cannot be adjusted (as to be increased), then the whole idea of creating a Quench Effect combustion chamber becomes diminished some.
What a bummer when it can be so important and helpful for a Marine SBC build.

FYI.... I began building SBCs in/around 1966 or so. At that time, most of them were HP auto engines.
I have never built one using anything but a quench style piston, giving me a quench effect combustion chamber.
I carried this practice over to the Marine world when I began doing Volvo Penta work.

Many times detonation damage is mis-diagnosed, even by the best Marine mechanics.

The 5.7L stroke is 3.480", whereas the 6.2L or 6.3L stroke is 3.750" .Pistons/rods are of the same approx mass, but are traveling at a greater velocity w/ the 3.750" stroke (not RPM, velocity!) and will stretch during the transition from approaching TDC to leaving TDC.
If things didn't stretch, the Q/E dimension could be almost ZERO.

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Rick is correct on the quench #s. Some racers run down to .025 on the piston to head clearance but that is with high tech high quality parts. Alot will run with .030 but they also know that catastrophe is possible but they are in it to win it.

For a everyday marine application .038 is good. Me personally on a 5.7 i do .035 but not sure it makes a difference i wont go less than that.

What you will notice with a good quench engine......

increased compression wont have detonation problems ( to a point)

improved torque and horsepower

Increased fuel economy to the point that the extra expense will pay for its self in fuel savings .

increased throttle response.

probably what you will notice most is in fuel savings and extra torque.

i run .035 with 10.8:1 with aluminum heads on pump gas regular.

I just pulled out 2 -454 330hp big blocks 2 weeks ago and getting ready to install 2- 350 small blocks 380 hp quench built run on regular pump gas.

Comment

Base timing is not adjustable, but the TA (total advance) can be...
still I would leave it alone, put everything back stock.
Also ECM 555 is working in conjunction with 2 knock sensors ( 1 per each bank ) to limit the spark advance to prevent detonation from occurring.

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Lineman, in spite of what some may suggest (building it in a standard fashion, etc), please understand that you will have a much better engine (6.3L stroker) if you build a quench effect into the combustion chamber!
You can work out the ignition advance issue later!

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Belive me I have read post 50 a few times. Changing timing and or fuel maps in the ecm is possible just expensive. Nobody makes a a tuner for the 555??? I understand just running the stock maps and timing curve I will gain torque and a few horsepower. I just wondering what I'm leaving on the table by not being able to play with timing or air/fuel ratios

Back to the machine shop.
Heads and block check out. With a surface job the heads end up at 61cc. Right now I'm looking at Autotec forged piston there
1000145 auto tech. 3.750 stroke, 5.700" rods, 4.030" bore, -18.9cc dome. Thay will cut the dome to -23.3 and with 61cc chambers it should come out to 9.3 to one CR. If I zero the deck and use the fel-pro marine head gaskit I think I end up with .042 quench. Have to get the parts and mock it up to be sure. Here's a pic of the piston profile
What do you all think so far.

Back to the machine shop.
Heads and block check out. With a surface job the heads end up at 61cc. Right now I'm looking at Autotec forged piston there
1000145 auto tech. 3.750 stroke, 5.700" rods, 4.030" bore, -18.9cc dome.Please explain "dome" to us!

They will cut the dome to -23.3First off, that piston should have NO dome to it.
The piston's deck will be at the same elevation as is the quench surface.

You DO NOT want them to cut the deck surface.
That would cause the need for a thinner head gasket in order to acquire the proper Q/E dimension.

and with 61cc chambers it should come out to 9.3 to one CR. If I zero the deck and use the fel-pro marine head gaskit I think I end up with .042 quench. Have to get the parts and mock it up to be sure. Here's a pic of the piston profile
What do you all think so far.

Since you are budgeting for a more expensive Forged Piston, you may as well go with a piston that offers reliefs for both Intake and Exhaust valves.
In other words, smaller reliefs for the exhaust valves, and the larger reliefs for the intake valves. This will increase the Q/E some.
This also means that your build would require 4 piston part numbers.

Shown below is a set of F/T pistons with specific size Int/Exh valve reliefs.
Example ONLY.

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Rick
I think were on the same page with the pistons take a look at the pic in my last post. It might be that Autotec is calling there piston dish a reverse dome?
On the deck height I'm not sure how far down the hole the piston sits yet. Cutting the deck would be dependent on piston placement and head gasket thickness In order to end up about .042 quench. With the - dish or dome setting setting C/R
As for the valve relives I understand what you're saying and I will have to ask.

1992 2452
5.0 alpha1 gen2

Comment

Rick
I think were on the same page with the pistons take a look at the pic in my last post. It might be that Autotec is calling there piston dish a reverse dome?Yes.... you will occasionally hear these called a "reverse dome".
What you actually want (or what I would want), would be a LCQ piston. (LCQ = low compression quench)

On the deck height I'm not sure how far down the hole the piston sits yet.Should be around no more than .015" leaving you with around .028" for the compressed head gasket thickness.

Cutting the deck would be dependent on piston placement and head gasket thickness In order to end up about .042 quench. With the - dish or dome setting setting C/R Standard SBC block deck height dimension should be 9.025".

As for the valve relives I understand what you're saying and I will have to ask.You could save a few $$ by going with a good hypereutectic material piston with the correct valve reliefs.
Not entirely necessary..... but I would do it!

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Autotec will custom cut the forged pistons cheaper than I can get Hypereutectic

Well, that is good!

They will most likely be of 2618 alloy.
They will expand at a greater rate, so your shop will very likely set them up more loosely than if they were the Hyperuetectics.

Your shop will also want to know a bit about your cooling system....... such as Raw Water cooled or fitted with a Closed Cooling system. (in other words, the most likely operating temperature).

Suggestion:

......While your new 400 harmonic balancer is not yet installed, have it marked off (engraved) in degrees from ZERO to approx 35 degrees BTDC.
......Then, during the assembly, ask the shop to perform a PPS and dial the ZERO line in to true #1 TDC.

Now you will be all set up to look at your dynamic ignition advance, and to see how close you can get your ignition system to offer the more desired 32* at/near 3,200 RPM.

And can we change your thread title to something like; "Some day it sucks to be me, and my 6.3L SBC build" ?

Comment

Pistons are a 4032 foraging . Degreing the balancer is a wonder idea Even if I cant move the timing curve at least I can see it. As for the title this thread started with water in 2 holes of my new to me 6.2. I don't know how to rename a post 1/2 or more of this thread should be called another 383 build.